This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-324388 filed on Oct. 24, 2000.
The present invention relates to a solar sensor.
A solar sensor has become an essential component in a zone-air-conditioning system that enables independent temperature control for each of passengers in the driver""s seat and in the passenger""s seat in a vehicle.
A solar sensor shown in FIG. 12 is proposed. The proposed sensor has a screen wall 102 between optical devices 100 and 101 to provide an output difference between optical devices 100 and 101 by means of attenuating or screening incident light irradiating to the far side optical device 101. Thereby, it is possible to detect solar azimuth angle.
Quantity of solar irradiation to a vehicle is constant irrespective of solar azimuth angle so that total output of optical devices 100 and 101 needs to be constant for controlling the zone-air-conditioning system. However, the total output is determined by total quantity of solar irradiation to optical devices 3 and 4 so that the total output is reduced when incident light is attenuated or screened by the screen wall 102.
This inconstancy in the total output in the proposed solar sensor becomes remarkable especially at low solar elevation angle. As shown in FIGS. 13a, 13b and 13c, the total output at 15xc2x0 of solar elevation angle varies significantly in accordance with solar azimuth angle while the total outputs at 75xc2x0 and 45xc2x0 of solar elevation angles do not vary significantly. For example, the total outputs at +90xc2x0 and xe2x88x9290xc2x0 of solar azimuth angles decrease by ca. 50% in comparison with the total output at 0xc2x0 of solar azimuth angle.
It is an object of this invention to provide a solar sensor that provides constant total output of optical devices in detecting quantity of solar irradiation irrespective of solar azimuth angle.
According to the present invention, a solar sensor includes an optical lens disposed above optical devices and a lens member disposed between the optical devices and the optical lens. The optical lens functions as a divergent lens and incident light spreading out from a concave formed on the optical lens irradiates a pair of projections formed on the lens member. The clearance between the concave and the projections in the direction of travel of a vehicle is larger than the clearance between the concave and the projections in the horizontally vertical direction to the direction of travel of a vehicle. Therefore, quantities of light irradiating to the projections are equally reduced by the optical lens in the case that incident light enters from the front side. However, in the case that incident light enters from the right or left side, the near side projection receives an unreduced quantity of light while the far side projection receives less light than in the case that the incident light enters from the front side. This is due to light divergence at the optical lens and interference of the near side projection with the light incident on the far side projection. As a result, a total quantity of light irradiating to the projections is the same in both cases. Thus, the total output of the left and right optical devices in a detection of quantity of solar irradiation becomes constant irrespective of solar azimuth angle.